With progress of time and continuous fast development of Internet Protocol (Internet Protocol, IP for short) services such as a third-generation (3rd-Generation, 3G for short) mobile communications service, Internet Protocol television (Internet Protocol Television, IPTV for short), video conferencing, streaming, and point-to-point (Point-to-Point, P2P for short), IP network traffic increases sharply, and Internet bandwidth demands have witnessed explosive growth. Internet traffic is doubled every 12 months over the recent years, but the capacity of a router is only doubled every 18 months. The speed at which the Internet traffic grows is far higher than that at which the capacity of equipment such as a router increases. Currently, available capacities of a single router and a core router in a cluster have exceeded levels of 1 Tbps and 100 Tbps respectively. Although further increase is possible, the development of the single router and cluster nodes is limited by maturity of optical components having high-rate ports. Furthermore, because of factors such as the power consumption of the single router and cluster nodes, heat dissipation, and bearing capacity of an equipment room, the single router and cluster nodes are unable to meet requirements of Internet traffic growth.
A supporting network and node corresponding to an IP service bearer network and node are a transport network and transport network node developed in parallel. The transport network and node not only undertake interconnection, transport, and bearing tasks between router nodes, but also undertake dedicated line services. Service development promotes generation and development of an all-optical switching technology. All-optical switching is mainly implemented by using passive optical components, and has a distinguishing characteristic of low power consumption. With respect to bearer networks and node technologies for IP and IP-like services, the industry and research circle put forward an optical packet switching/optical burst switching (Optical Packet Switching/Optical Burst Switching, OPS/OBS for short) concept and so on, seeking processing, switching, and buffering directly on optical signals. It is a pity that, in the current OPS/OBS concept, many key technologies, optical random storage/buffer components, and technologies and components for directly processing optical packets and optical burst headers in an optical domain can hardly achieve a breakthrough and cannot be put into practical commercial applications. Technologies in the OPS/OBS concept, due to data loss and reliability, are inapplicable to transport application scenarios that require high reliability. Currently, common transport networks mainly include a conventional synchronous digital hierarchy (Synchronous Digital Hierarchy, SDH for short), a synchronous optical network (Synchronous Optical Network, SONET for short), and an emerging optical transport network (Optical Transport Network, OTN for short). The emerging OTN is a mainstream technology in the current transport network, and will gradually replace the conventional SDH/SONET. With the development of services, a core transport node of the emerging OTN is also faced with a capacity requirement problem. In addition, compared with a router node, the core transport node of the emerging OTN is faced with a large-capacity requirement that is far higher than that of the router node. Generally, the required capacity of the core transport node of the OTN is several times to dozens of times that of a core router.
However, in implementation of the OTN and the core transport node of the OTN, total power consumption of a cabinet denotes a heat dissipation requirement at a corresponding level. Both density of heat generation and density of power consumption allowed by an equipment room are limited. Density of heat generation and density of power consumption allowed by a cabinet are also limited. As early as in 2003, the required maximum power consumption designed for a cabinet had reached 10 kw, but the average power supply capacity of equipment rooms at the time was designed to be 1.1 kw per cabinet, and the average power consumption in actual running was about 1.7 kw; capacities of 90% equipment rooms were designed to be 3 kw per cabinet, and the average power consumption in actual running was about 2 kw; the maximum capacity was designed to be 6 kw per cabinet, but the highest power consumption of a cabinet at the time had reached 12 kw. Currently, for a standard telecommunication equipment cabinet of 2200 mm (H)×600 mm (W)×600 mm (D), the total power consumption of the cabinet may reach about 20-24 kw, already far higher than an ultimate heat dissipation capability of each cabinet, that is, 4-6 kw in an equipment room with standard cabinet layout. This is equivalent to the power consumption and heat dissipation budget of 4 or 5 standard cabinets in the equipment room. In addition, limited by signal attenuation of a high-speed electrical backplane, a transmission distance of a single equipment can only reach 75 cm to 100 cm. To overcome the transmission distance problem, usually two equipments (chassis) are placed in such a cabinet; however, even if two equipments (chassis) are placed, the total capacity of the cabinet is only about 12.8T (typically, the capacity of each equipment is about 6.4T). Currently, switching of sub-wavelength bandwidth granularities smaller than the line bandwidth (2.5 G; 10 G; 40 G; 100 G) of an OTU-k depends on an electrical node of the OTN, but the capacity requirement of the electrical node of the OTN already reaches the P-level requirement of one P or several Ps. The conventional electrical node of the OTN is also constrained by factors such as the total power consumption of the cabinet, heat dissipation, and bearing capacity of the equipment room in the face of the P-level capacity requirement, and it is difficult to achieve a breakthrough. Therefore, a multi-chassis cluster becomes a future development direction of the OTN. For the electrical node of the OTN, to implement multi-chassis cascading, only optical or electrical interconnection or all-electrical switching can be adopted. All-electrical switching requires relatively high power consumption, which limits full playing of the cascading capability of multiple equipments. To resolve the problem of high power consumption in all-electrical switching, all-optical switching may be used to replace all-electrical switching. However, for all-optical switching, optical burst synchronization is critical to implementation of all-optical switching.